I don't mean in game terms, I mean real world terms. Brest and Marseille are far from the front and Brest's port facilities demolished. Since the Allies bombed the French Railways everything is coming by truck (I.e. The red ball express) and that stretches the supply line badly, this caused the Allies no end of supply problems during the fall and early winter until they cleared the scheldt.
Capturing Kiel is good and much better but I would assume the Germans would similarly demolish the port facilities in similar vein to Brest. Or at least mine the area enough to make it unusable for quite some time.
The game doesn't really capture these logistical dynamics nor air interdiction. I'm assuming the victory conditions are meant to compensate for these deficiencies. And we'll it is a learning scenario.
in 2011 we created a few house rules (see the file section)
the one about destruction of installation is:
Installation destruction by land units during movement phase
Add to 30.1:
Infantry and Armor units can automatically destroy an installation at the end of its movement phase if the unit was not activated during the turn, does not use rail movement, and ends the movement phase in the installation that should be destroyed.